Things to look for when using your Weck jars for canning:
(please keep checking back – I’ll be adding to this page as images and new information comes in)
Some visual cues to the relative sizes of small Weck jars:
Even when you are holding them in your hands, it can be hard to believe that this jar will hold exactly the same amount as that jar. These pictures may not be pretty (it was a quickie in answer to a customer’s question) – but the first does show a small Tulip (W762), small Deco (W902), and smallest Mold (W740) ALL holding 200 ml, and Mold styles W741 & W900 both holding 250 ml. The two mini-mold styles in the middle hold 2 oz or 1/4 cup (W080) and 4 oz or 1/2 cup (W760).
These jars all hold milk and were measured with a Pyrex fluids measuring cup (as opposed to a measuring cup meant to hold dry product such as sugar or flour).
They have varying head-space amounts; what is marked on the jar is what the jar contains. (Eventually I will remeasure W741 to see if it can actually hold 275 ml. Or perhaps it was just designed with a little extra head space.)
And, an example of just Weck styles holding 200 ml each (left to right, Tulip, Deco, and Mold):
Why to use extra clamps when pressure canning:
Weck jars are suitable for both hot-water-bath AND pressure canning. HOWEVER, pressure canning needs more clamps. Officially, I was told one, I prefer two (so four in total). Of course, you can use more if you wish! (Especially if you are using jars with the largest sized lid.) The idea is to place them symmetrically around the top of the jar to evenly exert pressure on the lid while canning.
This keeps the gasket in place and from “shooting out” in a spot and perhaps not sealing.
The clamps are on only during processing and the cool-down phase. The day after canning, remove the clamps and test the seal by lifting the jar an inch off the table by the lid. If the lid comes off, it didn’t seal. Also, as a visual cue, the tab on the gasket will point down, as if the jar is sticking it’s tongue out at you! 🙂
(As is usual, in the first few days after processing, you should carry out seal checks again, and always before you open each jar.)